The present invention relates to an image display medium, an image-forming method, an image-forming apparatus, and an initializer. More specifically, it relates to an image display medium capable of repetitive rewriting, an image-forming method in which an image is formed on the image display medium, an image-forming apparatus, and an initializer.
As a technology for displaying an image on so-called electronic paper, technologies such as twisting of color particles, electrophoresis, a thermal rewritable medium, a liquid crystal and electrochromy have been so far known. Of these technologies, there is an image display medium for conducting display with a toner in which a conductive color toner and white particles are interposed between a display substrate and a non-display substrate which are facing each other, and a charge-transferring layer is formed inside the non-display medium and a matrix electrode inside the display medium respectively. In such an image display medium, charges are injected in the conductive color toner through a charge transfer layer, and the conductive color toner in which charges are injected is moved by an electric field formed between substrates according to the image by the matrix electrode and is adhered to the display substrate. Consequently, the image as a contrast of the conductive color toner and the white particles is displayed on the display substrate.
Further, as an image display medium capable of repetitive rewriting, an image display medium using electrophoresis has been known (Kawai, Development of Electrophoresis Display Using Microcapsules, Nippon Gazoh Gakkai, Electronic Imaging Kenkyukai, p.31, 1999).
However, since the matrix electrode is employed in the image display medium using the toner, the medium cannot directly be applied to an ordinary image-forming apparatus in which an image is formed by developing an electrostatic latent image formed on an image carrier with a toner and transferring the same onto recording paper, such as a copier or a printer. In addition, the image display medium using the electrophoresis is problematic in that it is difficult to secure a safety of an insulating liquid or to provide a high-speed response.
The invention has been made to solve these problems, and provides an image display medium which satisfies a safety and a high-speed response and which is capable of repetitive rewriting, an image-forming method in which an image can be formed on the image display medium and which can be used in a copier or a printer in which an image is formed on recording paper, an image-forming apparatus, and an initializer.
According to an aspect of the invention, the invention provides an image display medium including a pair of substrates at least one of which has a charge-transporting property, and plural types of particle groups which are interposed movably by an electric field applied from outside and which are different in color and properties.
In this case, there is provided the image display medium in which between the pair of substrates at least one of which has the charge-transporting property, the particle groups movable by the electric field applied from outside, for example, an electric field generated by applying a DC voltage or an AC voltage between the substrates are interposed. These particle groups are different in color and properties. The properties are, for example, that the particles have a conductivity or an insulating property and the particles are charged positively or negatively. For example, according to another aspect of the invention, at least one type of the particle groups can be conductive particles. Since at least one of the substrates has a charge-transporting property, the particle groups can be charged by applying the electric field from outside.
Accordingly, the particle groups can be moved according to the image by applying the electric field according to the image to display the image by the contrast of the colors of the particle groups. Thus, the image can repetitively be displayed by applying the electric field from outside according to the image. At least two types of colors of the particle groups are sufficient. The particle groups may have a charge-transporting property.
An anisotropic conductive layer may be formed on the substrate having the charge-transporting property. Consequently, since the charges transferred are not spread widely, the thickness of the substrate can be increased.
The substrate having the charge-transporting property can be made of a charge-transferring polymer. Since the polymer is a self-supporting resin, a strong structure capable of enduring an external force given by bending or elongation can be provided.
Spacer particles having a diameter larger than the particles may be interposed between the substrates, whereby the distance between the substrates can be maintained approximately constant.
According to another aspect of the invention, the gap between the substrates can have a cell structure partitioned in a predetermined shape, whereby the distance between the substrates can be maintained approximately constant and partial imbalance of particles interposed between the substrates can be controlled to allow more stable image display.
According to another aspect of the invention, the conductive particles may be encapsulated in the cells according to plural colors forming a multicolor image. For example, conductive yellow particles and white particles, conductive magenta particles and white particles, and conductive cyan particles and white particles are encapsulated in the respective cells. The color image can be formed by generating the electric field according to each color.
According to another aspect of the invention, there is provided an image-forming apparatus for forming an image on an image display medium including a pair of substrates at least one of which has a charge-transporting property and plural types of particle groups which are interposed movably by an electric field applied from outside and which are different in color and properties, the image-forming apparatus including a latent image carrier, an electrostatic latent image forming unit for forming an electrostatic latent image adapted to the image on the latent image carrier, and a counter electrode for generating an electric field between it and the latent image carrier, the counter electrode being mounted in a position facing the latent image carrier such that the image display medium can be positioned therebetween.
In this case, the electrostatic latent image forming unit forms the electrostatic latent image adapted to the image on the latent image carrier. The counter electrode is mounted facing the latent image carrier such that the image display medium can be positioned therebetween. That is, the electric. field can be generated between the electrostatic latent image on the electrostatic latent image carrier and the counter electrode. Consequently, the particle groups interposed between the substrates can be moved by the electric field generated according to the image to form the image on the image display medium.
The electrostatic latent image forming unit may be so adapted that the latent image carrier is scanned with light beam adapted to the image to form the latent image adapted to the image on the latent image carrier. Further, the latent image carrier may be irradiated with ions generated by the ion-generating unit according to the image to form the electrostatic latent image adapted to the image on the latent image carrier. Still further, the electrostatic latent image adapted to the image may be formed on the latent image carrier by applying a high voltage to the stylus electrode to generate charge adapted to the image.
According to another aspect of the invention, a bias voltage is applied to the counter electrode, whereby an electric field can be generated in the opposite direction between the latent image carrier and the counter electrode. Therefore, for example, the particles adhered to the substrate on the counter electrode side can be moved to the substrate on the latent image carrier side, and the particles adhered to the substrate on the latent image carrier side to the substrate on the counter electrode side respectively.
According to another aspect of the invention, the apparatus has further a charging unit for previously charging the conductive particles.
In this case, the conductive particles can satisfactorily be moved between the substrates by previously charging the particles with the charging unit to display the image stably.
In the charging unit, at least one of a DC voltage and an AC voltage is applied to the substrates. When the DC voltage is applied to the substrates, the conductive particles can uniformly be adhered to one of the substrates. Thus, there is no need to apply bias to the counter electrode. Further, when the AC voltage is applied, the particles can satisfactorily be charged.
According to another aspect of the invention, it is also possible that the charging unit is made of an elastic material and at least one of a DC voltage and an AC voltage is applied to the substrates in a state closely adhered to the image display medium. Consequently, charges can be transferred well to the substrates to satisfactorily charge the particles.
According to another aspect of the invention, the substrate having a charge-transporting property is earthed before conducting the charging by the charging unit.
In this case, since the substrate having the charge-transporting property is earthed before conducting the charging by the charging unit, excess charges, when remaining in the particles, can be removed. Accordingly, it is possible to avoid strong adhesion of the particles to the substrate surface owing to excess charging and to apply stable charges to the particles.
According to another aspect of the invention, there is provided the image-forming apparatus which further includes an inputting unit for inputting whether the medium on which the image is formed is the image display medium or an image-recording medium, a developing unit for developing the electrostatic latent image formed by the electrostatic latent image forming unit with a toner when the result inputted by the inputting unit is the image-recording medium, a transferring unit for transferring the toner image developed by the developing unit onto the image-recording medium, and a fixing unit for fixing the toner image transferred onto the image-recording medium.
In this case, the inputting unit is for inputting whether the medium on which the image is formed is the image display medium or the image-recording medium, namely, ordinary recording paper. For example, a keyboard or a mouse can be used. Users can select the medium by this inputting unit. Further, the inputting unit may be a medium-detecting unit for detecting whether the medium on which the image is formed is the image display medium or the image-recording medium. In this instance, it is possible to detect which the medium is from an amount of reflected light by irradiating the medium with light. Moreover, it is also possible to detect which the medium is by detecting the weight.
In the developing unit, the electrostatic latent image formed by the electrostatic latent image forming unit is developed with the toner when the result inputted by the inputting unit is the image-recording medium, namely, ordinary recording paper. In the transferring unit, the toner image developed with the developing unit is transferred by applying, for example, a voltage to the image-recording medium. In the fixing unit, the toner image transferred onto the image-recording medium is fixed through, for example, heat fixing or pressure fixing.
The transferring unit may be a counter electrode. That is, the image formation of the image display medium and the image formation of the image-recording medium can be conducted with the same transferring unit, whereby the apparatus can be simplified and the costs can be reduced.
When the medium is the image display medium, the fixing treatment is dispensed with. Thus, according to another aspect of the invention, it is also possible that when the result inputted by the inputting unit is the image display medium, the fixing treatment by the fixing unit is not conducted. Consequently, the deterioration of the image display medium owing to heat can be prevented.
According to another aspect of the invention, the apparatus has further a development-stopping unit for stopping the development by the developing unit when the result inputted by the inputting unit is the image display medium.
In this case, the development-stopping unit stops the development when the result inputted by the inputting unit is the image display medium because there is no need to operate the developing unit. Further, when the developing unit is in an operable state, the toner on the electrostatic latent image carrier is supplied, and the image display medium is sometimes contaminated with the toner. Accordingly, when the development with the developing unit is stopped, the adhesion of the toner to the image display medium can be prevented.
In the development-stopping unit, the developing unit may be spaced apart from the latent image carrier, whereby the supply of the toner to the electrostatic latent image carrier can be prevented. Further, the rotation of the toner carrier included in the developing unit may be stopped. Still further, a voltage of reverse polarity to the potential of the electrostatic latent image may be applied to the toner carrier included in the developing unit. Furthermore, the supply of the toner to the toner carrier included in the developing unit may be stopped.
According to another aspect of the invention, the image display medium is initialized.
In this case, the image display medium is initialized, for example, the particles interposed between the substrates are charged before conducting the image formation. For example, a DC voltage, an AC voltage or a voltage obtained by superposing a DC voltage and an AC voltage is applied to the substrates. When the DC voltage is applied to the substrates, the conductive particles can uniformly be adhered to one of the substrates. Further, when the AC voltage is applied, the particles can satisfactorily be charged. Still further, the AC voltage and then the DC voltage may be applied. Consequently, the particles can satisfactorily be charged and the conductive particles be adhered to one of the substrates uniformly.